Soap production

ABSTRACT

A PROCESS FOR DIRECT PRODUCTION OF A SOAP OF WATER CONTENT NOT IN EXCESS OF 25% FOR HOUSEHOLD AND TOILET USES, BY SAPONIFICATION AT 120-180*C. UNDER 2-10 ATM. OF A FATTY ACID, NATURAL OR SYNTHETIC, USING AQUEOUS ALKALI SOLUTION OF CONTROLLED WATER CONTENT.

United States Patent 3,657,146 SOAP PRODUCTION Cornelis Willem Fransen, Utrecht, and Daniel Marten van Kampen, Vlaardingen, Netherlands, assignors to Lever Brothers Company, New York, N.Y.

No Drawing. Filed Nov. 1, 1968, Ser. No. 772,803 Claims priority, application Netherlands, Nov. 3, 1967, 6714945 Int. Cl. Clld 11/00, 13/00 U.S. Cl. 252-369 Claims ABSTRACT OF THE DISCLOSURE A process for direct production of a soap of water content not in excess of 25% for household and toilet uses, by saponification at 120-180 C. under 2-10 atm. of a fatty acid, natural or synthetic, using aqueous alkali solution of controlled water content.

The present invention relates to a process for preparing a soap of Water content not in excess of about 25% from fatty acids of natural or synthetic origin. It relates especially to soaps for toilet and household uses which desirably have respective water contents of about 15% and 22%.

Hitherto many soap preparation processes have involved a phase separation step or steps and result in a soap of 30% or more water content. Soaps of this high water content require a drying step to reduce the water to the abovementioned desirable levels. Some processes which allege production of soaps of the desirable low water contents are not operable with the fat charges, for example, used in toilet soaps in that the process specifies conditions of temperature and pressure under which the reactants mixture is viscous and is of non-pumpable consistency. To render these mixtures workable, more water has to be introduced resulting in a toilet soap of Water content in excess of about 27% which again requires a drying step.

The present invention concerns a process for the direct production of a soap including toilet soap and household soap having not more than water content, i.e. without a phase separation and without a subsequent drying step.

Accordingly, the present invention provides a process for the preparation of a soap by reaction of fatty acid with aqueous alkali solution at 120l80 C. and 2-10 atm. pressure and wherein the water content of the reactants is controlled to achieve the desired water content in the soap.

With the above ranges a temperature of less than 160 C. is preferred as is a pressure of under 6 atm. Reaction is effected in a pressure vessel or autoclave, with intensive stirring.

The preferred very intensive mixing achieves the almost immediate formation of soap which can be removed at once from the reaction space. The concentration of the alkali solution used according to the process of the invention varies between about 30 and 50%, dependent on the kind of soap to be prepared and the appertaining Water content. For soap with about 15% of water an alkali solution of about 50% is used, whereas for soap with about 20% of water an alkali solution with a concentration of about is used.

Under these process conditions all kinds of soap with the desired water content may be obtained in a direct way without applying any drying process, which soaps therefore are immediately suited to be e.g. milled and shaped into bars. The soaps to be processed, both normal and superfatted soaps, appear to have such a consistency that they are pumpable without difiiculty.

3,657,146 Patented Apr. 18, 1972 Addition of a small amount of sodium chloride solution may be advantageous for the consistency of the neat soap and for the characteristics of the final soap bar or the final soap tablet. The amount of NaCl required lies in most cases between 0.3 and 0.6%, calculated on the total weight of the final soap product. Consideration must be given to the quantity of water added to the reactants by way of solutions of additives e.g. NaCl.

The surprising aspect of the present invention is that at relatively low temperatures and at relatively low pressures soap can be obtained which is directly suited to be milled and shaped into bars.

The process according to the invention is suitable for the preparation of Na, K-, NH., and other metal soaps of fatty acids of varying compositions.

The process is particularly applicable to the processing of synthetic fatty acids into soap, which according to the normal boiling processes is often technically and/or economically impracticable. Using the normal boiling processes some blends of synthetic fatty acids tend to give soaps which separate to give lye and soap, or nigre and soap, which layers are of quite different compositions. Very often indeed losses of 20-25% of the fatty acid charge are observed in the saponification of synthetic fatty acids, due to the inevitable leaking of the more soluble synthetic fatty acid components, particularly the branched chain fatty acids, into the lye. The present process does not have such solubility/leaking problems.

The process according to the invention can be operated in a compact apparatus preferably a pressure vessel of not too large dimensions, e.g. of 60 litres content or smaller.

For carrying out the process of the invention an apparatus may be used consisting of a pressure vessel with heating device, provided with an intensively working stirring device, a number of dosing devices for alkali, fatty acid and if desired sodium chloride solution, and an outlet for the liquid neat soap to the cooling drums. A stirring device suitable for this purpose is eg. a disc rotor pump.

The advantage of the apparatus of the invention is also that it can be coupled without difficulty to a fatty acid distillation unit on the one side and to a continuous soap tableting line on the other side.

The invention will now be described by way of examples of the process according to the invention.

EXAMPLE 1 A 60 litre pressure vessel is provided with a Landustrie disc rotor immersion pump rotating at 3000 r.p.m. Via dosing devices stoichiometric amounts of 50% NaOH and a mixture of of tallow and 20% of coconut fatty acids, as well as a 23% sodium chloride solution in amount sufiicient to yield a soap having 03-06% NaCl content were pumped into this vessel, in which the temperature was kept at about 140 C. The pressure in the vessel was 4 atm. By the very intensive mixing. soap was formed at once, which through a Viking gear pump was pumped continuously to a cooling mill and formed into chips. The soap obtained had a water content of 15%.

To illustrate the specificity of the reaction conditions of the present invention the experiment was repeated using a temperature of C. and keeping the pressure at atmospheric level. Very bad mixing was observed in spite of the intensity of the mixing action probably due to the touch consistency of the autoclave contents. There was no suction of material into the gear pump. Increase of the temperature and pressure to C. and 1.5 atm. respectively, yielded easier mixing but the gear pump did not work smoothly.

A further experiment to show that additional water is necessarily present in the reactant mix, when the temperature and pressure conditions are not according to the pres ent invention, if a workable soap is to be obtained is as follows:

The following saponification process was carried out at 90 C. and at atmospheric pressure. 29 kg./h. fatty acid mixture consisting of 75% tallow and 25% coconut fatty acids, and 13.5 kg./h. 33% NaOH solution were pumped into a 60 litre pressure vessel provided with a Landustrie disc rotor immersion pump rotating at 3000 r.p.m. Through a separate dosing pump 1 k'g./h. 23% NaCl solution was added. The soap immediately obtained from the reaction vessel had a water content of approximately 30% and was of reasonable viscosity.

EXAMPLE 2 In the same pressure vessel as that of Example 1 were pumped with intensive stirring at 15.6 kg./h. of fatty acid mixture, consisting of 51.5% of tallow and 48.5% of coconut fatty acids, 4.58 kg./h. of a 50% N aOH solution and 0.44 kg./h. of a 23% NaCl solution. The pressure in the vessel was kept at 4 atm., and the internal temperature was about 140 C. Superfatted toilet soap was formed and pumped continuously through a gear pump to a cooling mill and formed into chips. The soap thus obtained contains 9% of free fatty acids as superfatting agent and 15% of water.

EXAMPLE 3 In the same pressure vessel as that of Example 1 were dosed at the prevailing temperature of 140 C. and a pressure of 4 atm. stoichiometrical amounts of synthetic fatty acid mixture of Q fatty acids, particularly C -C fatty acids, of which about 30% are branched. The acid number was 234-237. (18.9 kg./h.) and 50% NaOH solution (6.36 kg./h.) and 23% NaCl solution (0.65 kg./h.) was readily pumped continuously through a gear pump to a cooling mill and formed into chips. The water content of the soap was 12%.

EXAMPLE 4 1n the same pressure vessel as used in Example 1 were pumped with intensive stirring stoichiometric amounts of 50% NaOH and a mixture of 80% tallow and 20% coconut fatty acids. The temperature in the vessel was kept at 130 C. and the pressure was maintained at 4 atm. The process ran smoothly w-ithout difiiculty in mixing and pumping, giving soap with a water content of approximately 15 The process remained smooth on increasing the process conditions to 150 C. and 5.5 atm., and the water 4 content of the soap from the mill was approximately 15%.

EXAMP LES A fatty acid charge of tallow and 25% coconut fatty acids was saponified in the pressure vessel at C. and under a pressure of 2 atm. with 40% NaOH solution in stoiichiometric amounts.

The soap which was formed immediately was pumped from the vessel by a Viking gear pump, and had a water content of approximately 20% What is claimed is:

1. A continuous process for the direct production of soap suitable for milling and shaping into bars for toilet and household purposes, said soap having a predetermined moisture content of not more than 22%, compris ing intensive mixing of an at least stoichiometrically proportioned stream of fatty acids selected from the group consisting of coconut fatty acids, tallow fatty acids, C C synthetic fatty acids, and mixtures thereof, and a stream of aqueous sodium hydroxide solution of a concentration of 30-50%, while maintaining the reaction mixture under a pressure of about 210 atm., at a temperature of about 120180 C., and without a drying step.

2. A continuous process according to claim 1, wherein the aqueous sodium hydroxide is present in a 50% concentration and the reaction mixture is maintained under a pressure of 2-6 atm. at a temperature of 120-160.

3. A continuous process according to claim 1, wherein said soap has a moisture content of not more than 15 4. A continuous process according to claim 1, wherein said strea-ms of fatty acids are selected from the group consisting of tallow and coconut oil fatty acids and mixtures thereof.

5. A continuous process according to claim 1, wherein said streams of fatty acids are synthetic fatty acid mixtures having 7-25 carbon atoms.

References Cited UNITED STATES PATENTS 2,970,116 1/1961 Kelly et al. 252-368 2,753,363 7/1956 Winer 260-413 2,578,366 12/1951 Mills 252-367 2,159,397 5/1939 Mills 260-415 LEON D. ROSDOL, Primary Examiner D. L. ALBRECHT, Assistant Examiner US. Cl. X.R.

252-108, 132, 370, DIGEST 16; 260-413, 417 

